I. Field of the Invention
The present invention relates to mobile systems carrying rotatable mixing drums for mixing and dispensing concrete. More specifically, this invention relates to a helical mixing fin assembly for mixing and moving materials within concrete mixing drums that involves a superior fin structure and system for mounting the helical mixing fin assembly within rotatable drum mixers.
II. Related Art
Concrete mixing trucks are widely used in the construction industry for preparing and transporting concrete mix to desired construction sites. Such trucks feature a large rotatable mixing drum which includes fins or agitators mounted inside for mixing and directing the movement of a concrete mixture therein. Such fins typically have a helical configuration which will tend to mix concrete when the mixing drum is rotated in a first direction and urge the concrete towards a discharge chute when the mixing drum is turned in an opposite direction.
The mixing or agitation of materials such as concrete in a rotary mixing environment creates a great deal of abrasive friction between the mixing fins and the various abrasive components of the concrete mixture which is being transported. As a result, mixing fins have typically worn out long before the outer wall of the mixing drum itself and so the drums have had to be rebuilt or replaced sooner than desired. Accordingly, polymer-coated metal fins and mixing fins constructed of polymeric materials, particularly with internal reinforcing materials, have been developed. Mixing fin structures of the class have been shown, for example, in U.S. Pat. Nos. 5,056,924; 5,178,457; 5,378,061; and 5,427,449. While a degree of success has been achieved with such mixing fins, there remains a need for a helical or spiral mixing fin assembly that includes an improved mounting structure for use in concrete mixing drums of various materials.